This invention relates generally to vaporization systems, and more particularly, to methods and apparatus for operating vaporization systems.
Known conversion systems are utilized to process harmful or spent material into safe or useable material. At least some known conversion systems are utilized to process enriched uranium, or uranium hexafluoride (UF6) contained within transportation cylinders. These known systems include a vaporization system to heat and vaporize the material within the cylinders to a gas state. Once in the gas state, the material is channeled from the cylinders to a conversion reactor such that the material may be processed into a useable form.
At least some of these known vaporization systems include a first autoclave and a second autoclave for processing a first cylinder and a second cylinder, respectively. Additionally, a plurality of flow lines and flow valves are coupled to each autoclave for channeling the gas vapor to the conversion reactor. In operation of these known vaporization systems, the first cylinder is heated within the first autoclave and the material within the first cylinder is channeled through the vaporization system. A second cylinder is pre-heated and prepared for use. Once the flow and pressure from the first cylinder starts to decrease below a predetermined amount, the flow valves controlling the channeling of the vapor from the first cylinder are shut off. However, a small portion of the material remains in the flow lines and the first cylinder. As such, additional flow valves are opened to channel the remaining vapor in the first cylinder, also known as the heel, into a cold trap. Specifically, the cold trap operates at a temperature below the condensation temperature of UF6 and below the temperature of the first autoclave, and as such, a vacuum is created to channel the remaining vapor in the first cylinder to the cold trap. The cold trap process is operated until the first cylinder is empty. Once the first cylinder is empty, the first cylinder is removed from the first autoclave and is replaced with a new cylinder. While the remaining gas from the first cylinder is channeled to the cold trap, the flow valves for controlling the flow of the vapor from the second cylinder are opened. As such, the second cylinder is emptied in a similar manner as the gas from the first cylinder.
In these known vaporization systems, a continuous cycle of processing the uranium hexafluoride cylinders in the first autoclave and the second autoclave is performed until the cold trap is full. Once the cold trap is full, the cold trap is processed in a similar manner as the transportation cylinders in order to empty the cold trap. Specifically, the cold trap is heated and the material in the cold trap is vaporized. The vapor from the cold trap is channeled through a plurality of flow lines to the conversion reactor.
In these known vaporization systems, the conversion reactor receives zero flow of vapor as the system is switched over from processing the first autoclave to processing the second autoclave, and vice versa. Additionally, the conversion reactor receives zero flow of vapor as the system is switched over from processing the autoclaves to processing the cold trap. Specifically, it can take between a few minutes and a few hours to switch over between the different processes. As such, the conversion reactor is not utilized during this time. Additionally, in these known vaporization systems, the quality of product produced from the conversion process in the conversion reactor is varied due to the non-continuous flow of vaporized uranium hexafluoride. Specifically, the quality of product is affected by the pressure, flow rate, and concentration of uranium hexafluoride in the vapor. Each of these factors may be affected by the switch over of processing that occurs in known vaporization systems.